Can the permissions on a single appointment be changed?

I need to have an appointment created in one user's mailbox by another user
or custom app that does not allow the mailbox owner to change/delete the
appointment. If this is not possible, I need the changes to be logged. Does
anyone know if this can be done?

We need this because we want our scheduler to be able to add things to a
user's calendar, but we don't want the user to change the appointment. It
has to be the user's own mailbox calendar as we use BlackBerry Enterprise
Server 4.0 which does calendar sync with only the mailbox calendar.